In recent years, industrial demand for micro particles having various shapes is increased to thereby increase a market need for closely measuring physical properties of the micro particles, such as a particle size and shape.
For example, Patent literature 1 proposes a method and apparatus for measuring specific physical properties of micro particles on the basis of scattered light measurements using polarized light.
The apparatus described in Patent literature 1 is one that irradiates particles dispersed in a cell with polarized primary light such as laser light, and detects polarized light of scattered light of the primary light on a light receiving side to thereby measure a shape of the particles. According to the apparatus, on a light path from a light source to the cell, as illustrated in FIG. 1, optical elements are placed in the order of a convex lens 13, a polarizer 32, a half-wave retarder 33, a quarter-wave retarder 34, and also, before a light receiving element, optical elements are placed in the order of a half-wave retarder 35, a polarizer 36, and a convex lens 17.
In particular, in Patent literature 1, a light receiving optical system mechanism is configured to be rotatable around the cell, and adapted to be able to detect scattered light intensities having different angles with the single light receiving element. In the case of such a configuration, there are advantages of being able to facilitate a reduction in number of parts, and also of no instrumental error occurrence in the light receiving element in the dispersed in a cell with polarized primary light such as laser light, and detects polarized light of scattered light of the primary light on a light receiving side to thereby measure a shape of the particles. According to the apparatus, on a light path from a light source to the cell, as illustrated in FIG. 1, optical elements are placed in the order of a convex lens 13, a polarizer 32, a half-wave retarder 33, a quarter-wave retarder 34, and also, before a light receiving element, optical elements are placed in the order of a half-wave retarder 35, a polarizer 36, and a convex lens 17.
In particular, in Patent literature 1, a light receiving optical system mechanism is configured to be rotatable around the cell, and adapted to be able to detect scattered light intensities having different angles with the single light receiving element. In the case of such a configuration, there are advantages of being able to facilitate a reduction in number of parts, and also of no instrumental error occurrence in the light receiving element in the first place.
Meanwhile, a part where a light flux irradiated by the primary light and a detection angle based light flux on the light receiving side intersect with each other in the center of the cell corresponds to a part referred to as a scattering volume, and to arrange a pin hole having a diameter corresponding to the scattering volume before the detector to receive only scattered light is performed in this sort of particle characterization device. This is to enable the measurement to be performed at a high S/N ratio.
To cite above-described Patent literature 1, before the light receiving element, optical elements are placed in the order of a pin hole 19, a half-wave retarder 35, a polarizer 36, a convex lens 17, and a pin hole 31.
Meanwhile, in typical scattered light measurement, in order to detect intensities of a plurality of scattered lights that are scattered at different angles, a plurality of light receiving elements are provided; however, in Patent literature 1, the light receiving optical system mechanism is configured to be rotatable around the cell, and adapted to be able to detect scattered light intensities having different angles with the single light receiving element. In the case of such a configuration, there are advantages of being able to facilitate a reduction in number of parts, and also no instrumental error occurrence in the light receiving element in the first place.
Also, to configure the light receiving optical system mechanism to be rotatable, mechanical mechanism support parts such as a rail and a rotating plate are required in practice, and although some influence is present, the light receiving optical system mechanism itself is inevitably influenced by mechanical errors.
For this reason, there arises a problem that when the light receiving optical system is rotated to perform the measurements, at respective measurement angle positions, positions of a light flux of secondary light with respect to the pin hole are different, and detected light amounts at the respective measurement angle positions are varied.
However, in this sort of particle characterization device, depending on an angle and polarization direction of scattered light, scattered lights having an extremely wide intensity range from a very intense scattered light to a very weak scattered light may occur, and therefore the single light receiving element configuration as in Patent literature 1 may not cover the intensity range. Also, the apparatus described in Patent literature 1 uses a number of optical elements related to polarization and the like, which causes cost increase, and also many unexpected troubles may occur, such as a reduction in transmittance, occurrence of stray light, increase in number of adjustment places.
Also, in the case of measuring a particle size by a dynamic light scattering method, a preferred scattering angle depends on a concentration of a liquid sample, and in the case where the liquid sample concentration is low, 90° is preferable, whereas in the case where the liquid sample concentration is high, 180° is preferable; however, in the case of measuring the liquid sample concentration in advance, work becomes cumbersome, and in the case of a trace amount of sample, a loss of the sample also becomes a problem.
Further, in the case where the liquid sample concentration is extremely high, even if the measurement is performed at the scattering angle of 180°, a sufficient amount of scattered light cannot be received, which may make it difficult to perform the measurement with high accuracy.
Also, conventionally, regarding physical properties of nano particles, shape-related physical property values such as an aspect ratio (horizontal to vertical ratio) and an agglomeration level, a particle size, and a dispersion level are respectively measured by using separate analyzers, i.e., by observations using an electron microscope such as a scanning electron microscope (SEM) or an optical microscope, by the dynamic light scattering method, and by measuring a zeta potential.
However, to measure the respective physical property values with the separate analyzers, a sufficient amount of liquid sample is required, and in the case where an amount of the liquid sample is trace in the range of a few μm to a few tens μm, the amount of the sample is short, and therefore the required analyses may not be performed.
Also, in the case of using the electron microscope or optical microscope, the shape-related physical property values and particle size are calculated as image processing results; as measurement results for the case of using the particle size distribution measuring device, the particle size and particle size distribution are respectively presented as a numerical value and a histogram; and in the case of using a zeta potential measuring device, the zeta potential is presented as a numerical value or distribution. The zeta potential refers to a surface charge of a micro particle in a solution, i.e., a potential on a “sliding plane” on which liquid flow starts to occur in an electric double layer formed around the micro particle in the solution. In the case of the micro particle, as an absolute value of the zeta potential increases, repulsive force between the particles is increased to enhance stability of the particles. On the other hand, as the zeta potential approaches zero, the particles are likely to agglomerate. That is, depending on a charge amount (charge state) of the particles, stability of a dispersion state of the particles is varied, and therefore to control the agglomeration/dispersion of the micro particles in the solution and characterize the micro particles, an importance level of the zeta potential measurement is increased.
However, although results of such measurements can be easily interpreted if a measurer is familiar with principles of the devices, it may be difficult for one unfamiliar with the measurements to interpret meanings of obtained numerical values and distributions.    [Patent literature 1] U.S. Pat. No. 6,721,051    [Patent literature 2] JP 2004-317123 A    [Patent literature 3] JP 2004-271287 A